import os
import sys
from optparse import OptionParser
from imp import find_module

import django
from django.core.management.base import BaseCommand, CommandError, handle_default_options

# For backwards compatibility: get_version() used to be in this module.
get_version = django.get_version

# A cache of loaded commands, so that call_command
# doesn't have to reload every time it's called.
_commands = None

def find_commands(management_dir):
    """
    Given a path to a management directory, returns a list of all the command
    names that are available.

    Returns an empty list if no commands are defined.
    """
    command_dir = os.path.join(management_dir, 'commands')
    try:
        return [f[:-3] for f in os.listdir(command_dir)
                if not f.startswith('_') and f.endswith('.py')]
    except OSError:
        return []

def find_management_module(app_name):
    """
    Determines the path to the management module for the given app_name,
    without actually importing the application or the management module.

    Raises ImportError if the management module cannot be found for any reason.
    """
    parts = app_name.split('.')
    parts.append('management')
    parts.reverse()
    path = None
    while parts:
        part = parts.pop()
        f, path, descr = find_module(part, path and [path] or None)
    return path

def load_command_class(app_name, name):
    """
    Given a command name and an application name, returns the Command
    class instance. All errors raised by the import process
    (ImportError, AttributeError) are allowed to propagate.
    """
    return getattr(__import__('%s.management.commands.%s' % (app_name, name),
                   {}, {}, ['Command']), 'Command')()

def get_commands(load_user_commands=True, project_directory=None):
    """
    Returns a dictionary mapping command names to their callback applications.

    This works by looking for a management.commands package in django.core, and
    in each installed application -- if a commands package exists, all commands
    in that package are registered.

    Core commands are always included. If a settings module has been
    specified, user-defined commands will also be included, the
    startproject command will be disabled, and the startapp command
    will be modified to use the directory in which that module appears.

    The dictionary is in the format {command_name: app_name}. Key-value
    pairs from this dictionary can then be used in calls to
    load_command_class(app_name, command_name)

    If a specific version of a command must be loaded (e.g., with the
    startapp command), the instantiated module can be placed in the
    dictionary in place of the application name.

    The dictionary is cached on the first call and reused on subsequent
    calls.
    """
    global _commands
    if _commands is None:
        _commands = dict([(name, 'django.core') for name in find_commands(__path__[0])])

        if load_user_commands:
            # Get commands from all installed apps.
            from django.conf import settings
            for app_name in settings.INSTALLED_APPS:
                try:
                    path = find_management_module(app_name)
                    _commands.update(dict([(name, app_name) for name in find_commands(path)]))
                except ImportError:
                    pass # No management module -- ignore this app.

        if project_directory:
            # Remove the "startproject" command from self.commands, because
            # that's a django-admin.py command, not a manage.py command.
            del _commands['startproject']

            # Override the startapp command so that it always uses the
            # project_directory, not the current working directory
            # (which is default).
            from django.core.management.commands.startapp import ProjectCommand
            _commands['startapp'] = ProjectCommand(project_directory)

    return _commands

def call_command(name, *args, **options):
    """
    Calls the given command, with the given options and args/kwargs.

    This is the primary API you should use for calling specific commands.

    Some examples:
        call_command('syncdb')
        call_command('shell', plain=True)
        call_command('sqlall', 'myapp')
    """
    try:
        app_name = get_commands()[name]
        if isinstance(app_name, BaseCommand):
            # If the command is already loaded, use it directly.
            klass = app_name
        else:
            klass = load_command_class(app_name, name)
    except KeyError:
        raise CommandError, "Unknown command: %r" % name
    return klass.execute(*args, **options)

class LaxOptionParser(OptionParser):
    """
    An option parser that doesn't raise any errors on unknown options.

    This is needed because the --settings and --pythonpath options affect
    the commands (and thus the options) that are available to the user.
    """
    def error(self, msg):
        pass

class ManagementUtility(object):
    """
    Encapsulates the logic of the django-admin.py and manage.py utilities.

    A ManagementUtility has a number of commands, which can be manipulated
    by editing the self.commands dictionary.
    """
    def __init__(self, argv=None):
        self.argv = argv or sys.argv[:]
        self.prog_name = os.path.basename(self.argv[0])
        self.project_directory = None
        self.user_commands = False

    def main_help_text(self):
        """
        Returns the script's main help text, as a string.
        """
        usage = ['%s <subcommand> [options] [args]' % self.prog_name]
        usage.append('Django command line tool, version %s' % django.get_version())
        usage.append("Type '%s help <subcommand>' for help on a specific subcommand." % self.prog_name)
        usage.append('Available subcommands:')
        commands = get_commands(self.user_commands, self.project_directory).keys()
        commands.sort()
        for cmd in commands:
            usage.append('  %s' % cmd)
        return '\n'.join(usage)

    def fetch_command(self, subcommand):
        """
        Tries to fetch the given subcommand, printing a message with the
        appropriate command called from the command line (usually
        "django-admin.py" or "manage.py") if it can't be found.
        """
        try:
            app_name = get_commands(self.user_commands, self.project_directory)[subcommand]
            if isinstance(app_name, BaseCommand):
                # If the command is already loaded, use it directly.
                klass = app_name
            else:
                klass = load_command_class(app_name, subcommand)
        except KeyError:
            sys.stderr.write("Unknown command: %r\nType '%s help' for usage.\n" % \
                (subcommand, self.prog_name))
            sys.exit(1)
        return klass

    def execute(self):
        """
        Given the command-line arguments, this figures out which subcommand is
        being run, creates a parser appropriate to that command, and runs it.
        """
        # Preprocess options to extract --settings and --pythonpath.
        # These options could affect the commands that are available, so they
        # must be processed early.
        parser = LaxOptionParser(version=get_version(), option_list=BaseCommand.option_list)
        try:
            options, args = parser.parse_args(self.argv)
            handle_default_options(options)
        except:
            pass # Ignore any option errors at this point.

        try:
            subcommand = self.argv[1]
        except IndexError:
            sys.stderr.write("Type '%s help' for usage.\n" % self.prog_name)
            sys.exit(1)

        if subcommand == 'help':
            if len(args) > 2:
                self.fetch_command(args[2]).print_help(self.prog_name, args[2])
            else:
                sys.stderr.write(self.main_help_text() + '\n')
                sys.exit(1)
        # Special-cases: We want 'django-admin.py --version' and
        # 'django-admin.py --help' to work, for backwards compatibility.
        elif self.argv[1:] == ['--version']:
            # LaxOptionParser already takes care of printing the version.
            pass
        elif self.argv[1:] == ['--help']:
            sys.stderr.write(self.main_help_text() + '\n')
        else:
            self.fetch_command(subcommand).run_from_argv(self.argv)

class ProjectManagementUtility(ManagementUtility):
    """
    A ManagementUtility that is specific to a particular Django project.
    As such, its commands are slightly different than those of its parent
    class.

    In practice, this class represents manage.py, whereas ManagementUtility
    represents django-admin.py.
    """
    def __init__(self, argv, project_directory):
        super(ProjectManagementUtility, self).__init__(argv)
        self.project_directory = project_directory
        self.user_commands = True

def setup_environ(settings_mod):
    """
    Configures the runtime environment. This can also be used by external
    scripts wanting to set up a similar environment to manage.py.
    Returns the project directory (assuming the passed settings module is
    directly in the project directory).
    """
    # Add this project to sys.path so that it's importable in the conventional
    # way. For example, if this file (manage.py) lives in a directory
    # "myproject", this code would add "/path/to/myproject" to sys.path.
    project_directory, settings_filename = os.path.split(settings_mod.__file__)
    if project_directory == os.curdir or not project_directory:
        project_directory = os.getcwd()
    project_name = os.path.basename(project_directory)
    settings_name = os.path.splitext(settings_filename)[0]
    sys.path.append(os.path.join(project_directory, os.pardir))
    project_module = __import__(project_name, {}, {}, [''])
    sys.path.pop()

    # Set DJANGO_SETTINGS_MODULE appropriately.
    os.environ['DJANGO_SETTINGS_MODULE'] = '%s.%s' % (project_name, settings_name)
    return project_directory

def execute_from_command_line(argv=None):
    """
    A simple method that runs a ManagementUtility.
    """
    utility = ManagementUtility(argv)
    utility.execute()

def execute_manager(settings_mod, argv=None):
    """
    Like execute_from_command_line(), but for use by manage.py, a
    project-specific django-admin.py utility.
    """
    project_directory = setup_environ(settings_mod)
    utility = ProjectManagementUtility(argv, project_directory)
    utility.execute()
